https://www.gamespot.com/articles/fortnite-update-adds-vending-machines-weapon-chang/1100-6457925/

Epic Games has revealed the latest additions coming to Fortnite. But unlike in the past, this won't come as part of a new update you have to download; instead, it's like a delayed rollout for the contents of the previous patch. The first such "content update," as Epic calls them, has arrived on all platforms and introduces the Vending Machine, among other changes and additions.

Each material type--wood, stone, and metal--will have a corresponding item that it can be exchanged for. The vending machine will display one at a time and slowly rotate through them. To buy what you want, you can either wait for it to show up, or you can hit the Vending Machine with your pickaxe to skip to the next of the three items. They don't always appear in the same locations, but we have a guide to finding Vending Machines.